Amides of deacetylcolchicine and deacetylisocolchicine with dihydrofluorescein diacetate have been prepared as potential markers of the colchicine binding site on tubulin. (14)C-labeled isothiocyanato- deacetylthiocolchicine did not prove to be useful to specifically mark the colchicine binding site. Total synthesis of two ring A dimethoxy substituted dibenzocycloheptatrienes revealed that all 3 methoxy groups in the ring A of colchicine are important for the interaction with proteins. Optically active isomers of N-acetyl- colchinol methyl ether with the acetamido group at C(5) did not bind to tubulin.